Magnesium base alloy



' Patented Jan. 13, 1942 MAGNESIUM Bass ALLOY John C. McDonald, Midland,Mich assignor to The Dow Chemical Company, Midland, Mich a corporationof Michigan No Drawing. Application December 23, 1940,

Serial No. 371,377 1 3 Claims.

The invention relates to magnesium base alloys and more particularlyconcerns an alloy of this nature having a high' degree of formabilityassociated' with other desirable physical properties, such as improvedtensile and yield strengths.

Magnesium base alloys are being widely used in the structural arts wherea light weight metal is highly desirable, such as for use in makingcastings, forgings, and the like. However, the use of these alloys inthe rolled form to make sheet metal articles requiring formingoperations, such as bending and drawing has not progressed as rapidlydue to the fact that, in general, alloys having good formability orductility permitting properties is found in those alloys having from 3to 8 per cent of silver, 3 to 6 per cent of aluminum,- to per cent ofcadmium, 0.2 per cent of cerium, and 0.2 to 0.5 per cent of manganese.

The following table, listing some of the properties of rolled sheetmetal made from my new polynary alloy and comparing these propertieswith those of some related parent alloys, illustrates the improvement inyield and tensile 10 strengths of the new alloy. Further the per centelongation which is to be regarded as a measure of the formability ofthe alloy is of a high order and thus renders the alloy suitable for usein connection with conventional forming operations.

Table Nominal composition in percent I (magnesium-remainder) AnnealedCold rolled Percent Yield Tensile Yield .Tensile Ag Al Ce Cd Mn elontion strength in strength in strength in strength in in 2 ches lbs./sq.in. lbs/sq. in. lbs./sq. in. lhsJsq. in.

relatively sharp bends to be made without the article developingexternal cracks, usually have inferior characteristics as regards theirtensile and yield strengths.

It is, accordingly, the principal object of the invention to provide amagnetism base alloywhich can be made into rolled "sheet andthe likepossessing a suflicient degree of ductility or formability at ordinarytemperatures to be sharply bent, drawn or otherwise shaped, while havinggood tensile and yield strengths.

Other objects and advantages will be apparent as the description of theinvention proceeds.

My invention resides in the discovery that a magnesium base alloycontaining from about 0.3

to 10 per cent of silver, 0.3. to 10 per cent of aluminum, 1 to per centof cadmium, 0.01"to1 per cent of cerium, and from 0.01 to l'per cent ofmanganese possesses the aforementioned desirable properties. The termmagnesium used herein and in the appended claims is intended to includemagnesium containing the ordinary impurities found in the commerciallypure metal, such as traces of iron, nickel, copper and silicon. Whilethe property of excellent formability associated with\ high tensile andyield strengths-is manifest overthe entire range of compositionindicated, the most desirable combination of position,

The properties set forth above under the term annealed wereobtained byfirst rolling the alloys at a temperature of 550 F. and thereafterannealing them at various temperatures through a-range of from 400 to800 F. The properties selected for the table were those of the annealedspecimens which exhibited the maximum alongation. The properties setforth under the term coldgrolled were obtained by subjecting specimensof the alloys which had first been hot rolled at a temperature of 550 F.to additional rolling in the cold state. The properties selected for the0 table were those of the cold rolled specimens which showed thegreatest tensile and yield strengths, while having at least a l per centelongation in 2 inches. .From a comparison of the properties listed inthe table it will be-seen that the tensile strength and 'yleldstrengt-hin both the annealed and cold rolled state are superior to those of therelated alloys. At the same time it will be observed that the per centelongation which serves as a measure of the ductility is of a sumcientlyhigh order to. enable the alloy to readily undergo forming operations,such as bendingfdrawing,

- and the like without danger of developing cracks.

The improvement shown by the particular comillustrated in the table, isexhibited throughout the percentage range of the alloying ingredientindicated.

While the new alloy is most useful in wrought form, such as sheets dueto its formability characteristics, it may also be used for makingcastings, extruded forms. and the like. It is further pointed out thatmy new alloy is amenable to solution and precipitation heat treatments,which accordingly modify its properties.

The new alloy may be compounded in any of the ways usually employed formelting and alloying metals with magnesium such as by adding thealloying ingredients singly or jointly to a bath of molten magnesiumwhich is preferably protected from oxidation by a suitable flux.

Cerium may be added to the alloy as such, or in the form of Misch-metal.Magnesium-cerium alloys are commonly made up by employing Misch-metal asa source of cerium. It is sometimes desirable to add more than thetheoretical amount of Misch-metal since the alloying efficiency is notalways 100 per cent and some loss may be incurred.

It should be mentioned that the amount of manganese that maybe presentin a given composition is dependent upon the amount of aluminum present.For example, when about 0.5

per cent aluminum is present, it is difficult to obtain an alloycontaining more than 1.0 per cent of manganese. In compositionscontaining more aluminum, such as from 8 to 10 per cent, it is diflicultto obtain an alloy containing more than about 0.5 per cent of manganese.

It is to be understood that the invention is not limited to the specificcomposition herein described, but may take other forms without departingfrom the scope of the invention.

I claim:

1. A magnesium base alloy containing from about 0.3 to '10 per cent ofsilver, 0.3 to 10 per cent of aluminum, 1 to 15 per cent of cadmium,0.01 to 1 per cent of cerium, and from 0.01 to 1 per cent of manganese,the balance being magnesium.

2. A magnesium base alloy containing from about 3 to 8 per cent ofsilver, 3 to 6 per cent of aluminum, 5 to 10 per cent of cadmium, 0.2per cent of cerium, and from 0.2 to 0.5 per cent'oi" manganese, thebalance being magnesium.

3. A magnesium base alloy containing from about 0.3 to 10 per cent ofsilver, about 0.3 to 10 per cent of aluminum, about 1 to 15 per cent ofcadmium, about 0.01 to 1 per cent of cerium, and

about 0.01 to 1 per cent of manganese and characterized by highlyimproved yield strength and tensile strength in the cold rolled state ascom- 'pared to a similar magnesium-silver-aluminumcadmium-manganesealloy devoid of cerium.

JOHN C. MCDONALD.

